Dozer and Fel were never "loose leash" walkers.
Fel, in fact, was such an incorrigible puller that one of our area's top trainers, confident only minutes before that he could stop her pulling immediately, muttered "She's a tough case, eh" as she yanked him along, oblivious to his various tactics. It was something of an understatement. He gave up on her before too long, and so did I; she wore a Gentle Leader head harness from then on, and that stopped the pulling, for the most part. Once she got old and sick, the walks got a lot easier.
Dozer is not a well-trained loose leash walker. He hates walking, so it's more of a cowed slink; the leash is loose because he doesn't want to go very fast. Show him something interesting, and he darts ahead. He also surges forward when a car passes, as if he's trying to keep up with it, or maybe hitch a ride back home without me.
Star may be the redeeming dog here. We have been relentlessly training loose leash walking since day 2 (I let her do what she wanted on day 1, just to see). For a while, I doubted my ability to train loose leash, considering my poor track record. Sure, I can teach a dog to put toys in a toy box and close cabinet doors, but walking? But Star is learning--fast. This is the serious "heel," too, not the "as long as you're somewhere nearby" type of loose leash. It's kind of neat.
I'm using the "circle" technique to train. Basically, as soon as the dog gets too far ahead, out of the range you specify, you turn around and walk the other way. The dog goes "what the?" and turns and follows, and you reward as soon as the dog reaches the "heel" position. Then you circle back around and continue on with your walk. The first several times, the reward is probably delivered as the dog runs past to pull ahead (at which point you turn around again), but after a while, the dog realizes the reward comes from staying beside the walker's leg. Furthermore, the circling around causes the dog to focus on the walker (to avoid collision at the very least).
Then it's just a matter of constant reward for the "heel" position, slowly delivering the treats at a less-frequent interval as the dog "gets it," and at a more frequent interval if a challenging/distracting situation arises, such as barking dogs or people walking by. There's no punishment involved, unless you consider it punishment to walk in circles (I sure do--I get dizzy after a while!).